Golf balls having multi-layer cores are known. For example, U.S. Pat. No. 6,852,044 discloses golf balls having multi-layered cores having a relatively soft, low compression inner core surrounded by a relatively rigid outer core. U.S. Pat. No. 5,772,531 discloses a solid golf ball comprising a solid core having a three-layered structure composed of an inner layer, an intermediate layer, and an outer layer, and a cover for coating the solid core. U.S. Patent Application Publication No. 2006/0128904 also discloses multi-layer core golf balls. Other examples of multi-layer cores can be found, for example, in U.S. Pat. Nos. 5,743,816, 6,071,201, 6,336,872, 6,379,269, 6,394,912, 6,406,383, 6,431,998, 6,569,036, 6,605,009, 6,626,770, 6,815,521, 6,855,074, 6,913,548, 6,981,926, 6,988,962, 7,074,137, 7,153,467 and 7,255,656.
The present invention provides a novel multi-layer core golf ball construction wherein the core comprises a thermoset rubber inner core, a thermoset rubber first intermediate core layer, a thermoplastic second intermediate core layer, and a thermoset rubber outer core layer.